There is an increasing interest in reducing energy consumption in wireless communication networks, both from an environmental perspective contributing to a sustainable world, but also from the perspective of reducing operational expenditure. With ever increasing energy costs, there is a strong operator demand for solutions that enable decreased energy consumption without affecting throughput in the network.
An example of a wireless communication network in which power saving initiatives have been investigated is the Long Term Evolution, LTE, network. The LTE comprises a new radio interface and new radio access network architecture. The LTE radio access network, RAN, uses a flat architecture with a single type of radio access node, the eNodeB, responsible for all radio related functions in one or several cells. In the LTE, the eNodeB is a logical node. A common physical implementation of an eNodeB is a three-sector site, where a radio base station is handling transmissions in three cells. In the following, the terms radio access node, eNodeB and RBS will be used in an interchangeable manner. The radio access node is the main power consumer in the radio access network.
LTE supports downlink transmission using up to four cell specific antenna ports. Each antenna port comprises or is connected to a power amplifier and physical antenna elements. If an LTE radio access node has more than one antenna port, it may be possible to mute one or more antenna ports when the traffic is low, thus reducing the power consumption in the radio access node.
WO2011/105938 discloses an approach for antenna muting in a wireless network wherein downlink power consumption is reduced in a radio base station. A solution is disclosed, where the radio base station is capable of working in a muted antenna mode, wherein a subset of antenna ports associated with the radio base station are muted when a measured load falls below a defined load value.
With said prior art solution, control of energy consumption in the radio base station may be improved by introducing an antenna mode with one or more muted antenna ports. However, there is a need for a solution addressing improving performance reliability when switching between antenna modes in a radio access node configured for muting and un-muting of antenna ports.